Add base:: to string16s in win8/.

win8/metro_driver/chrome_app_view.h

Index: win8/metro_driver/chrome_app_view.h
diff --git a/win8/metro_driver/chrome_app_view.h b/win8/metro_driver/chrome_app_view.h
index 0554ab31366860c7ea4a1e941c67b5278ca8673a..77d67815924bf098ae5d826ddd5ce86e7e89c6c5 100644
--- a/win8/metro_driver/chrome_app_view.h
+++ b/win8/metro_driver/chrome_app_view.h
@@ -155,8 +155,8 @@ struct Globals {
   HANDLE host_thread;
   ChromeAppView* view;
   WNDPROC g_core_proc;
-  string16 navigation_url;
-  string16 search_string;
+  base::string16 navigation_url;
+  base::string16 search_string;
   winapp::Activation::ApplicationExecutionState previous_state;
   winapp::Activation::ActivationKind initial_activation_kind;
   bool is_initial_activation;
@@ -164,7 +164,7 @@ struct Globals {
   // to be initiated from that thread, notably spawning file pickers.
   base::MessageLoopProxy* appview_msg_loop;
   winapp::Core::ICoreApplicationExit* app_exit;
-  string16 metro_command_line_switches;
+  base::string16 metro_command_line_switches;
 };
 
 extern Globals globals;